Question

A chemist has 100ml of 25% acid solution. How much of the solution does she need to drain and replace with 70% acid solution to obtain 100ml of 60% acid solution?

Answer 1

Answer:

The chemist must drain 78 g of 25% acid solution and replace with 78 g of 70% acid.

Step-by-step explanation:

• x= mass of the 25% acid the chemist must drain,
• Then we have,
• x= the mass, m of the 70% acid,
• 100-x=the mass of the 25% acid remaining,
• The operating equation is,
• Mass of acid in 25% + Mass of acid in 70%= Mass of acid in 60%,
• 0.25(100-x)+0.70 x=0.60×100,
• 25 - 0.25 x 0.70 x=60,
• 0.45 x= 35,
• x= 35/0.45,
• so we get,
• x=78 g.

Answer 2

Answer:

50% of the solution

Step-by-step explanation:

25% of 100 ml = 25

added to 70 % of (100 - x) = 70 - 0.7x

we need to add 25 + 70-0.7x to get = 100 ml 60% i.e 60

now,

solve for x

0.7x =25+70-60

0.7x =35

x = 35/0.7

x= 50 % of the solution she needs to drain